Thermal spreader for heat pipe coolers and water coolers

ABSTRACT

This invention relates to thermal spreader incorporated into heat pipe coolers and water coolers for electronic components, said spreader having optimal aspect ratio T/(√S)≧0.17 to provide optimal parameters of thermal resistance and lowering noise created by these coolers supplying by operating fans, where T is thickness of said thermal spreader and (√S) is square root of the surface area of the first surface of said thermal spreader. Further, the invention relates to electronic systems comprising said thermal spreader with optimal aspect ratio T/(√S)≧0.17 to provide better thermal management of electronic components incorporated into these electronic systems.

TECHNICAL FIELD

The present invention relates to cooling elements for dissipating heatfrom an electronic component in electronic devices.

BACKGROUND OF THE INVENTION

Electronic devices generate heat during normal operation. It is known inelectronic equipment to provide cooling systems to keep the electroniccomponent within a range of prescribed operating temperature. Coolingsystems of different types including heat pipe coolers and water coolersare used for cooling electronic components. An active fan is oftenmounted on top of the heat pipe and water coolers to transfer heat froma heat source to the ambient air. Overall thermal resistance of heatpipe and water coolers depends on both design of the cooler and airflowproduced by the fan.

Some cooling systems comprise a thermally conductive base or thermalspreader that spreads heat from the microprocessor to a heat dissipatingelement such as heat pipe and water cooler, and the heat dissipatingelement dissipate the heat to the air stream. We found that there is anoptimal aspect ratio of the thermal spreader to provide optimal heattransfer through the thermal spreader and, thus, minimize thermalresistance of heat pipe coolers and water coolers. This ratio isT/(√S)≧0.17, where T is thickness of said thermal spreader and (√S) issquare root of the surface area of the surface of said thermal spreader.The thermal spreader of this optimal ratio T/(√S)≧0.17 is unknown fromthe art and has never been used to decrease thermal resistance of heatpipe coolers and water coolers. Because of minimizing thermal resistanceof coolers by the use of the thermal spreader having the ratioT/(√S)≧0.17, it is now possible to decrease air flow generated byoperating fan and nevertheless keep the electronic component within arange of prescribed operating temperature. Accordingly, it is nowpossible to reduce fan rotation speed and, thus, to reduce noisegenerated by operating fan, since the noise of operating fan isproportional to the fan rotation speed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a thermal spreader of the inventionaccording to some embodiments.

FIG. 2A is a perspective view of a heat pipe cooler of the inventionaccording to some embodiments.

FIG. 2B is a cross-sectional view of a heat pipe cooler of the inventionaccording to some embodiments.

FIG. 3A is a perspective view of a water cooler of the inventionaccording to some embodiments.

FIGS. 3B and 3C are cross sectional views of the water block accordingto some embodiments.

FIG. 4 is a schematic side view of an electronic system according tosome embodiments, which incorporates the heat pipe cooler of FIG. 2.

FIG. 5 is a schematic side view of an electronic system according tosome embodiments, which incorporates the water cooler of FIG. 3.

FIG. 6 is a perspective view of heat pipe cooler used in measurements ofdependence of thermal resistance and noise levels on the ratio T/(√S) ofthe thermal spreader.

FIG. 7 is a graph of change of thermal resistance of heat pipe cooler ofFIG. 6 with operating fan versus ratio T/(√S) of the thermal spreaderaccording to some embodiments.

FIG. 8 is a graph of change of noise generated by operating fan of heatpipe cooler of FIG. 6 versus ratio T/(√S) of the thermal spreaderaccording to some embodiments.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a thermal spreader having a first surfaceto be thermally coupled to an electronic component and an opposingsecond surface to be thermally coupled to a heat dissipation deviceselected from the group consisting of a heat pipe cooler and a watercooler, wherein a ratio T/(√S)≧0.17, where T is thickness of saidthermal spreader and (√S) is square root of the surface area of thefirst surface of said thermal spreader.

In some embodiments, the thermal spreader of the invention ismanufactured from thermally conductive material, such as, but notlimited to, copper, silver, aluminium, and alloys thereof, and graphite.

FIG. 1 is a perspective view of a thermal spreader of the inventionaccording to some embodiments. The embodiments of the thermal spreader 1include, but are not limited to, thermal spreaders 1 a, 1 b, and 1 c.All such thermal spreaders have a first surface and an opposing secondsurface, wherein a ratio T/(√S)≧0.17, where T is thickness of saidthermal spreader and (√S) is square root of the surface area of thefirst surface of said thermal spreader. For the thermal spreaders 1 aand 1 b, the surface area of the rectangle first surface is calculatedby equation S=L·W, where L is length and W is width of the spreader. Forthe thermal spreader 1 c, the surface area of the circular first surfaceis calculated by equation S=πD²/4, where D is diameter of the thermalspreader.

Further, the present invention provides a heat pipe cooler for anelectronic component comprising: (1) a thermal spreader having a firstsurface to be thermally coupled to an electronic component and anopposing second surface; (2) at least one heat pipe thermally coupled tosaid second surface of said thermal spreader; (3) a plurality of finsfixed to said heat pipe; and (4) a fan for supplying the heatdissipating element with ambient air, wherein a ratio T/(√S)≧0.17, whereT is thickness of said thermal spreader and (√S) is square root of thesurface area of the first surface of said thermal spreader.

FIG. 2A is a perspective view and FIG. 2B is a cross-sectional view of aheat pipe cooler of the invention according to some embodiments. Thecooler 2 comprises the thermal spreader 1 having a ratio T/(√S)≧0.17,where T is thickness of said thermal spreader and (√S) is square root ofthe surface area of the first surface of said thermal spreader. Thecooler 2 also comprises a plurality of heat pipes 3 are thermallycoupled to the thermal spreader 1; a plurality of fins 4 mounted on saidheat pipes; and the fan 5 for supplying the fins 4 with ambient air. Theheat pipe cooler 2 is thermally coupled to an electronic component 6mounted on a mounting frame 7. The screws 8 secure the heat sink 1 ontothe electronic component 6.

Further, the present invention provides a water cooler for an electroniccomponent comprising: (1) a thermal spreader having a first surface tobe thermally coupled to an electronic component and an opposing secondsurface; (2) a water block thermally coupled to said second surface ofthe thermal spreader to transfer a heat from said thermal spreader; (3)a radiator connected with water block by water pipes; (4) a fan forsupplying radiator with ambient air; and (5) a pump for forcing waterthrough the cooling circuit consisting of the water block and theradiator, said pump is connected by water pipes with the water block andthe radiator, wherein a ratio T/(√S)≧0.17, where T is thickness of saidthermal spreader and ('IS) is square root of the surface area of thefirst surface of said thermal spreader.

FIG. 3A is a perspective view of a water cooler of the inventionaccording to some embodiments. The water cooler 13 includes a thermalspreader 1 thermally coupled to an electronic component 10 mounted on amounting frame 24, a water block 9 thermally coupled to the thermalspreader to transfer heat from the thermal spreader 1, a water pump 11,and a radiator 12. The water block 9 has a water outlet 14 and a waterinlet 15. A pipe 16 is connected between the water inlet 15 and a wateroutlet 17 of the water pump 11. Another pipe 23 is connected between thewater outlet 14 and a water inlet 18 of the radiator 12. The radiator 12is composed of multiple fins 19. A pipe 20 is connected between a wateroutlet 21 of the cooler 12 and a water inlet 22 of the water pump 11.Thus, a cooling circuit of the water cooler 13 is built. In application,colder water is fed into the water block 9 from the water pump 11. Afterheat exchange, the water is heated by electronic component 10 throughthe thermal spreader 1 into warmer water. The warmer water which flowsinto the radiator 12 will be cooled down. Thereby, the colder water thenflows back to the water pump 11 to supply the water circulation. FIGS.3B and 3C are cross sectional views of the water block 9 according tosome embodiments. Heat generated from the electronic component 10 isconducted to the water of the water block 9 via the thermal spreader 1having a ratio T/(√S)≧0.17, where T is thickness of said thermalspreader and (√S) is square root of the surface area of the firstsurface of said thermal spreader. The cooler water flows into the waterinlet 15 and further flows through the water outlet 14. Such that, thewater is heated by the electronic component 10 to take away the heat ofthe electronic component 10.

Further, the present invention provides an electronic system comprising:a substrate; an electronic component mounted on the substrate; a heatpipe cooler for an electronic component comprising: (1) a thermalspreader having a first surface to be thermally coupled to an electroniccomponent and an opposing second surface; (2) at least one heat pipethermally coupled to said second surface of said thermal spreader; (3) aplurality of fins fixed to said heat pipe; and (4) a fan for supplyingthe heat dissipating element with ambient air, wherein a ratioT/(√S)≧0.17, where T is thickness of said thermal spreader and (VS) issquare root of the surface area of the first surface of said thermalspreader. Preferably, the substrate is a circuit board. Preferably, theelectronic component is selected from the group consisting of amicroprocessor and a graphics processor. Preferably, the system isselected from the group consisting of a personal computer and mediacenter.

FIG. 4 is a schematic side view of an electronic system according tosome embodiments, which incorporates the heat pipe cooler of FIG. 2. Theelectronic system 25 includes the substrate 26, the electronic component27 mounted on the substrate 26, and the heat pipe cooler 28 comprising athermal spreader 1 thermally coupled to an electronic component, thethermal spreader having a ratio T/(√S)≧0.17, where T is thickness ofsaid thermal spreader and (√S) is square root of the surface area of thefirst surface of said thermal spreader.

Further, the present invention provides an electronic system comprising:a substrate; an electronic component mounted on the substrate; watercooler for an electronic component comprising: (1) a thermal spreaderhaving a first surface to be thermally coupled to an electroniccomponent and an opposing second surface; (2) a water block thermallycoupled to said second surface of the thermal spreader to transfer aheat from said thermal spreader; (3) a radiator connected with waterblock by water pipes; (4) a fan for supplying radiator with ambient air;and (5) a pump for forcing water through the cooling circuit consistingof the water block and the radiator, said pump is connected by waterpipes with the water block and the radiator, wherein a ratioT/(√S)≧0.17, where T is thickness of said thermal spreader and (√S) issquare root of the surface area of the first surface of said thermalspreader.

FIG. 5 is a schematic side view of an electronic system according tosome embodiments, which incorporates the water cooler of FIG. 3. Theelectronic system 29 includes the substrate 30, the electronic component31 mounted on the substrate 30, and the water cooler 32 comprising athermal spreader 1 thermally coupled to an electronic component, thethermal spreader having a ratio T/(√S)≧0.17, where T is thickness ofsaid thermal spreader and ('IS) is square root of the surface area ofthe first surface of said thermal spreader.

In some embodiments, the electronic systems 25 and 29 are selected fromthe group consisting of a personal computer and media center.

In some embodiments, the electronic component may be a conventionalpackaged IC (integrated circuit). For example, the electronic component,may be a processor such as any type of computational circuit, includingbut not limited to a microprocessor, a microcontroller, a complexinstruction set computing (CISC) microprocessor, a reduced instructionset computing (RISC) microprocessor, a very long instruction word (VLIW)microprocessor, a graphics processor, a digital signal processor (DSP),or any other type of processor or processing circuit.

The electronic systems 25 and 29 may also include a number of othercomponents which are not shown in the drawing. These components areinclude, but are not limited to, a chip set and/or a communicationcircuit which may be functionally coupled to the electronic component, adigital switching circuit, a radio frequency (RF) circuit, a memorycircuit, a custom circuit, an application-specific integrated circuit(ASIC), an amplifier, an external memory in the form of one or morememory elements, RAM (random access memory) and/or ROM (read onlymemory), one or more hard drives and/or one or more drives that handleremovable media such as floppy diskettes, compact disks (CDs), digitalvideo disks (DVDs), and so forth all of these components may befunctionally coupled to the electronic component.

Still other components (not shown) may be included in the electronicsystems 25 and 29 such as a display device, one or more speakers, and akeyboard and/or controller, which can include a mouse, trackball, gamecontroller, speech recognition device or any other device that permits auser to input information into and/or receive information from theelectronic systems. Each of these devices, too, may be functionallycoupled to the electronic component.

It should be understood that the electronic systems 25 and 29 need notbe a personal computer, but may alternatively be a server computer or agame device.

Because of the use of the thermal spreader having the ratio T/(√S)≧0.17,it is now possible to decrease thermal resistance of heat pipe coolersand water pipe coolers. Because of minimizing thermal resistance ofcoolers of the invention by the use of the thermal spreader having theratio T/(√S)≧0.17, it is now possible to decrease air flow generated byoperating fan and nevertheless keep the electronic component within arange of prescribed operating temperature. Accordingly, it is nowpossible to reduce fan rotation speed and, thus, to reduce noisegenerated by operating fan, since the noise of operating fan isproportional to the fan rotation speed.

FIG. 6 is a perspective view of heat pipe cooler used in measurements ofdependence of thermal resistance and noise levels on the ratio T/(√S) ofthe thermal spreader. The cooler 33 comprises the thermal spreader 1;two heat pipes 34 thermally coupled to the thermal spreader 1; aplurality of fins 35 mounted on heat pipes 34; and the fan 36 forsupplying the fins 35 with ambient air. The cooler 33 is thermallycoupled to a heat source mounted on a mounting frame 37.

FIG. 7 is a graph of change of thermal resistance of heat pipe cooler ofFIG. 6 with operating fan versus ratio T/(VS) of the thermal spreaderaccording to some embodiments. The thermal resistance of the heat pipecooler was is measured for the thermal spreader 1 of variable height andconstant the length and the width, and under otherwise equal conditions.As found, desirable low values of the thermal resistance is achievedwhen the ratio T/(√S)≧0.17. Thus, the thermal resistance of the heatpipe cooler is minimized with the thermal spreader of optimal ratioT/(√S).

FIG. 8 is a graph of change of noise generated by operating fan of heatpipe cooler of FIG. 6 versus ratio T/(√S) of the thermal spreaderaccording to some embodiments. The noise created by operating fan wasmeasured under the fixed thermal resistance of 0.6° C./watt. The noisevalue was regulated by rotation speed of operating fan 36. The thermalspreader 1 of variable height and constant the length and the width wasused. As found, desirable low values of the noise is achieved when theratio T/(√S)≧0.17. Thus, the noise of operating heat pipe cooler can beminimized with the thermal spreader of optimal ratio T/(√S).

The several embodiments described herein are solely for the purpose ofillustration and are not intended to limit the scope of the invention inany way. The various features described herein need not all be usedtogether, and any one or more of those features may be incorporated in asingle embodiment. Therefore, persons skilled in the art will recognizefrom this description that other embodiments may be practiced withvarious modifications and alterations.

1. A thermal spreader having a first surface to be thermally coupled toan electronic component and an opposing second surface to be thermallycoupled to a heat dissipation device selected from the group consistingof a heat pipe cooler and a water cooler, wherein a ratio T/(√S)≧0.17,where T is thickness of said thermal spreader and (√S) is square root ofthe surface area of the first surface of said thermal spreader.
 2. Aheat pipe cooler for an electronic component comprising: (1) a thermalspreader having a first surface to be thermally coupled to an electroniccomponent and an opposing second surface; (2) at least one heat pipethermally coupled to said second surface of said thermal spreader; (3) aplurality of fins fixed to said heat pipe; and (4) a fan for supplyingthe heat dissipating element with ambient air, wherein a ratioT/(√S)≧0.17, where T is thickness of said thermal spreader and (√S) issquare root of the surface area of the first surface of said thermalspreader.
 3. A water cooler for an electronic component comprising: (1)a thermal spreader having a first surface to be thermally coupled to anelectronic component and an opposing second surface; (2) a water blockthermally coupled to said second surface of the thermal spreader totransfer a heat from said thermal spreader; (3) a radiator connectedwith water block by water pipes; (4) a fan for supplying radiator withambient air; and (5) a pump for forcing water through the coolingcircuit consisting of the water block and the radiator, said pump isconnected by water pipes with the water block and the radiator, whereina ratio T/(√S)≧0.17, where T is thickness of said thermal spreader and(√S) is square root of the surface area of the first surface of saidthermal spreader.
 4. An electronic system comprising: a substrate; anelectronic component mounted on the substrate; a heat pipe cooler for anelectronic component comprising: (1) a thermal spreader having a firstsurface to be thermally coupled to an electronic component and anopposing second surface; (2) at least one heat pipe thermally coupled tosaid second surface of said thermal spreader; (3) a plurality of finsfixed to said heat pipe; and (4) a fan for supplying the heatdissipating element with ambient air, wherein a ratio T/(√S)≧0.17, whereT is thickness of said thermal spreader and (√S) is square root of thesurface area of the first surface of said thermal spreader.
 5. Theelectronic system of claim 4, wherein the substrate is a circuit board.6. The electronic system of claim 4, wherein said electronic componentis selected from the group consisting of a microprocessor and a graphicsprocessor.
 7. The electronic system of claim 4, wherein the system isselected from the group consisting of a personal computer and mediacenter.
 8. An electronic system comprising: a substrate; an electroniccomponent mounted on the substrate; water cooler for an electroniccomponent comprising: (1) a thermal spreader having a first surface tobe thermally coupled to an electronic component and an opposing secondsurface; (2) a water block thermally coupled to said second surface ofthe thermal spreader to transfer a heat from said thermal spreader; (3)a radiator connected with water block by water pipes; (4) a fan forsupplying radiator with ambient air; and (5) a pump for forcing waterthrough the cooling circuit consisting of the water block and theradiator, said pump is connected by water pipes with the water block andthe radiator, wherein a ratio T/(√S)≧0.17, where T is thickness of saidthermal spreader and (√S) is square root of the surface area of thefirst surface of said thermal spreader.
 9. The electronic system ofclaim 8, wherein the substrate is a circuit board.
 10. The electronicsystem of claim 8, wherein said electronic component is selected fromthe group consisting of a microprocessor and a graphics processor. 11.The electronic system of claim 8, wherein the system is selected fromthe group consisting of a personal computer and media center.